Sequential Coordination Function for Throughput and Fairness Enhancement of Wireless LANs

High throughput and fair resource sharing are two of the most important objectives in designing a medium access control (MAC) protocol. Currently, most MAC protocols including IEEE 802.11 DCF adopt a random access based approach in a distributed manner in order to coordinate the wireless channel accesses among competing stations. In this paper, we first identify that a random access?Cbased MAC protocol may suffer from MAC protocol overhead such as a random backoff for data transmission and a collision among simultaneously transmitting stations. Then, we propose a new MAC protocol, called sequential coordination function (SCF), which coordinates every station to send a data frame sequentially one after another in a distributed manner. By defining a service period and a joining period, the SCF eliminates unnecessary contentions during the service period, and by explicitly determining the sequence of frame transmission for each stations, it reduces collision occurrences and ensures fairness among stations in the service period. The performance of SCF is investigated through intensive simulations, which show that the SCF achieves higher throughput and fairness performances than other existing MAC protocols in a wide range of the traffic load and the number of stations.